Transcript Slide 1

Re-Examination of Visions for
Tokamak Power Plants –
The ARIES-ACT Study
Farrokh Najmabadi
Professor of Electrical & Computer Engineering
Director, Center for Energy Research
UC San Diego
and the ARIES Team
TOFE 2012
August 30, 2012
ARIES Program Participants
Systems code: UC San Diego, PPPL
Plasma Physics: PPPL , GA, LLNL
Fusion Core Design & Analysis: UC San Diego, FNT Consulting
Nuclear Analysis: UW-Madison
Plasma Facing Components (Design & Analysis): UC San Diego, UWMadison
Plasma Facing Components (experiments): Georgia Tech
Design Integration: UC San Diego, Boeing
Safety: INEL
Contact to Material Community: ORNL
Goals of ARIES ACT Study
 Over a decade since last tokamak study : ARIES-1 (1990)
through ARIES-AT(2000).
 Substantial progress in understanding in many areas.
 New issues have emerged: e.g., edge plasma physics, PMI,
PFCs, and off-normal events.
o What would be the maximum fluxes that can be handled by invessel components in a power plant?
o What level of off-normal events are acceptable in a commercial
power plant?
 Evolving needs in the ITER and FNSF/Demo era:
 Risk/benefit analysis among extrapolation and attractiveness.
 Detailed component designs is necessary to understand R&D
requirements.
Frame the “parameter space for
attractive power plants” by considering
the “four corners” of parameter space
Reversed-shear
(βN=0.04-0.06)
DCLL blanket
Reversed-shear
(βN=0.04-0.06)
SiC blanket
1st Stability
(no-wall limit)
DCLL blanket
1st Stability
(no-wall limit)
SiC blanket
ARIES-RS/AT
SSTR-2
EU Model-D
Physics
Extrapolation
Higher power density
Higher density
Lower current-drive power
Lower power density
Lower density
Higher CD power
Lower thermal efficiency
Higher Fusion/plasma power
Higher P/R
Metallic first wall/blanket
Engineering
performance
(efficiency)
ARIES-1
SSTR
Higher thermal efficiency
Lower fusion/plasma power
Lower P/R
Composite first wall/blanket
Status of the ARIES ACT Study
 Project Goals:
 Detailed design of advanced physics, SiC blanket ACT-1
(ARIES-AT update).
 Detailed design of ACT-2 (conservative physics, DCLL
blanket).
 System-level definitions for ACT-3 & ACT-4.
 ACT-1 research will be completed by Dec. 2012.
 First design iteration was completed for a 5.5 m Device.
 Updated design point at R = 6.25 m (detailed design on-going)
 9 papers in this conference.
 ACT-2 Research will be completed by June 2013.
ARIES-ACT1 (ARIES-AT update)
 Advance tokamak mode
 Blanket: SiC structure & LiPb Coolant/breeder
(to achieve a high efficiency)
ARIES Systems Code – a new
approach to finding operating points
 Systems codes find a single
operating point through a
minimization of a figure of
merit with certain constraints
 Very difficult to see sensitivity
to assumptions.
 Our new approach to systems
analysis is based on surveying
the design space and finding a
large number of viable
operating points.
 A GUI is developed to
visualize the data. It can
impose additional constraints
to explore sensitivities
Example: Data base of operating points with
fbs ≤ 0.90, 0.85 ≤ fGW ≤ 1.0, H98 ≤ 1.75
Impact of the Divertor Heat load
 Divertor design can handle > 10 MW/m2
peak load.
 UEDGE simulations (LLNL) showed
detached divertor solution to reach high
radiated powers in the divertor slot and
a low peak heat flux on the divertor
(~5MW/m2 peak).
 Leads to ARIES-AT-size device at

R=5.5m.
Control & sustaining a detached divertor?
 Using Fundamenski SOL estimates and
90% radiation in SOL+divertor leads to
a 6.25-m device with only 4 mills cost
penalty (current reference point).
 Device size is set by the divertor heat flux
The new systems approach
underlines robustness of the design
point to physics achievements
Major radius (m)
6.25
6.25
Aspect ratio
4
4
Toroidal field on axis (T)
6
7
Peak field on the coil (T)
11.8
12.9
5.75%
4.75%
Plasma current (MA)
10.9
10.9
H98
1.65
1.58
Fusion power (MW)
1813
1817
Auxiliary power
154
169
Average n wall load (MW/m2)
2.3
2.3
Peak divertor heat flux (MW/m2)
10.6
11.0
Cost of Electricity (mills/kWh)
67.2
68.9
Normalized beta*
* Includes fast a contribution of ~ 1%
The new systems approach
underlines robustness of the design
point to physics achievements
Major radius (m)
6.25
6.25
Aspect ratio
4
4
Toroidal field on axis (T)
6
7
Peak field on the coil (T)
11.8
12.9
5.75%
4.75%
Plasma current (MA)
10.9
10.9
H98
1.65
1.58
Fusion power (MW)
1813
1817
Auxiliary power
154
169
Average n wall load (MW/m2)
2.3
2.3
Peak divertor heat flux (MW/m2)
10.6
11.0
Cost of Electricity (mills/kWh)
67.2
68.9
Normalized beta*
* Includes fast a contribution of ~ 1%
Detailed Physics analysis has been
performed using the latest tools
New physics modeling
 Energy transport assessment: what is






required and model predictions
Pedestal treatment
Time-dependent free boundary
simulations of formation and
operating point
Edge plasma simulation (consistent
divertor/edge, detachment, etc)
Divertor/FW heat loading from
experimental tokamaks for transient
and off-normal*
Disruption simulations*
Fast particle MHD
* Discussed in the paper by C. Kessel, this session
Overview of engineering design:
1. High-hest flux components*
 Design of first wall and divertor options
 High-performance He-cooled W-alloy

divertor, external transition to steel
Robust FW concept (embedded W pins)
 Analysis of first wall and divertor
options
 Birth-to-death modeling
 Yield, creep, fracture mechanics
 Failure modes
 Helium heat transfer experiments
 ELM and disruption loading responses
 Thermal, mechanical, EM &
ferromagnetic
* Discussed in papers by M. Tillack and J. Blanchard,
this session
Overview of engineering design*:
2. Fusion Core
 Features similar to ARIES-AT
 PbLi self-cooled SiC/SiC breeding blanket
with simple double-pipe construction
 Brayton cycle with h~60%
 Many new features and improvements
 He-cooled ferritic steel structural ring/shield
 Detailed flow paths and manifolding for
PbLi to reduce 3D MHD effects**
 Elimination of water from the vacuum
vessel, separation of vessel and shield
 Identification of new material for the
vacuum vessel***
* Discussed in the paper by M. Tillack, this session
** Discussed in the paper by X. Wang, this session
*** Discussed in the paper by L. El_Guebaly, this session
Detailed safety analysis has highlighted
impact of tritium absorption and transport
 Detailed safety modeling of ARIES-AT (Petti et al) and
ARIES-CS (Merrill et al, FS&T, 54, 2008 ) have shown a
paradigm shift in safety issues:
 Use of low-activation material and care design has limited

temperature excursions and mobilization of radioactivity
during accidents. Rather off-site dose is dominated by
tritium.
For ARIES-CS worst-case accident, tritium release dose is
8.5 mSv (no-evacuation limit is 10 mSV)
 Major implications for material and component R&D:
 Need to minimize tritium inventory (control of breeding,
absorption and inventory in different material)
 Design implications: material choices, in-vessel
components, vacuum vessel, etc.
In summary …
 ARIES-ACT study is re-examining the tokamak power plant
space to understand risk and trade-offs of higher physics and
engineering performance with special emphais on PMI/PFC
and off-normal events.
 ARIES-ACT1 (updated ARIES-AT) is near completion.
 Detailed physics analysis with modern computational tools are
used. Many new physics issues are included.
 The new system approach indicate a robust design window for this
class of power plants.
 Many engineering imporvements: He-cooled ferritic steel structural
ring/shield, Detailed flow paths and manifolding to reduce 3D MHD
effects, Identification of new material for the vacuum vessel …
 In-elastic analysis of component including Birth-to-death modeling
and fracture mechanics indicate a higher performance PFCs are
possible. Many issues/properties for material development &
optimization are identified.
Thank you!